Twenty-five years after her banishment from Fairyland for marrying a mortal, a crime usually punishable

by death, Iolanthe has been pardoned. She had a son by this illicit marriage, Strephon, who is, therefore, half mortal and half fairy. He is in love with Phyllis whom he is determined to marry. However, in order to do so he needs the consent of her guardian, the Lord Chancellor, who shows little enthusiasm for the idea of his ward marrying a mere shepherd. When Strephon turns to his mother for comfort, Phyllis misinterprets their intimacy (as a fairy Iolanthe has not physically aged beyond a certain point) and, believing him to be unfaithful, she renounces her love for him. Although he protests that Iolanthe is his mother, his claims are met with derision by Phyllis and the peers (who are unaware of his parentage) and even the intervention of the Queen of the Fairies cannot persuade them otherwise. Furious at their attitude, she declares that Strephon will enter Parliament and will work to overthrow all the privileges enjoyed by the nobility, a job at which Strephon is successful. However, he finds it no substitute for Phyllis and, with no further reason to conceal it, he reveals his fairy origins to her. This explains Iolanthe’s apparent youth and the couple become re-engaged. At Strephon’s request, Iolanthe puts their case to the Lord Chancellor, but has to disguise herself before doing so as, unbeknown to him, he is her mortal husband and she is forbidden to enlighten him under pain of death. Unfortunately, when he declares that he has decided to marry Phyllis himself, she is forced to reveal her true identity although this will mean forfeiting her life. However, when it emerges that the other fairies have committed the ultimate offence and married the peers (ie mortals), the Lord Chancellor suggests that the law be amended so that it is a crime for any fairy not to marry a mortal. The Queen happily selects a mortal for herself and invites the whole company to join her in Fairyland.